Deployment Vessel Research Articles

Vector acoustic observations of underwater noise energetics over a 24 h period in Puget Sound, Washington, as influenced by ferry and ship traffic

Vector acoustic measurements of underwater noise made continually over a 24-h period within a small bay on the west side of Puget Sound, Washington State are discussed. The bay contains the Washington State ferry landing at Kingston with measurement site approximately 1 km distant from the landing, at water depth 42 m. Periodic, nearby ferry traffic, and episodic large-vessel shipping activity punctuate the observations which will be compared with those made in deeper waters. Potential and kinetic energies in key shipping decidecimal bands are equal within calibration uncertainty; a practical result towards the inference of kinematic properties from pressure-only measurements within inland waters complementing similar results obtained in off shore waters. An important exception exists when the noise field is dominated by a vessel passing directly over the sensor, as was demonstrated by the deployment vessel moving at speed 7.5 knots. Observed near the seafloor, broadband noise emissions from a vessel passing directly above exhibit frequency bands where potential acoustic energy is greater than kinetic energy (and vice versa in neighboring frequency bands). This phenomenon is also examined with a model based on multiple interfering reflections from the seabed, sea surface, and buried sediment layers.

Measurements of tidal flow variability in Ramsey Sound, Pembrokeshire

The nature of the flow at in-stream tidal energy sites is particularly important for predicting array and device performance, and also for operations and maintenance planning. Previous developers have reported issues such as the choice of vessel, cost of operations, and the limits of operation of deployment vessels. The dynamics of the flow around slack water has been of particular interest at Ramsey Sound in Pembrokeshire (UK) for planning the recovery of an existing turbine, the Tidal Energy Limited ‘Deltastream’.
 This research presents flow characteristics of Ramsey Sound, based on analysis of Acoustic Doppler Current Profiler (ADCP) measurements and tide gauge data from the nearby Standard Port of Milford Haven. The ADCP was located approximately 300 m across the channel, at the northern end of the channel, where the channel width was 1200 m and the mean depth was approximately 33 m. The flow dynamics were examined specifically to look at times potentially suitable for offshore operations Two weeks of data were used in the analysis, spanning a complete spring-neap cycle.
 Results demonstrate that flow velocities exhibited clear asymmetry, with stronger flows on the northerly directed flood tide than on the ebb. There was considerable variation in the measured current speed around the time of the maximum, suggesting large scale bed feature generated turbulence. The flood (northerly) current maximum was approximately in phase with high water at Milford Haven. Cross correlation indicated that the flow generally led the elevation by 20 minutes. In contrast to the expected theory, the current strength at mid-depth was stronger than at the surface on the maximum flood tide. The maximum flow speed in the tide was reasonably predictable from the tide range at Milford. A threshold-based analysis of the ADCP measurements allowed the duration of slow-moving water to be identified for operation planning.
 Operations and planning in light of sound understanding of hydrodynamics at tidal energy sites is critical for future economic success of the tidal energy sector. The results shown here from an ADCP deployment in Ramsey Sound have shown the capability to give useful tools for planning recovery operations.

Effects of acute angle, proximal bending, and distal bending in the deployment vessels on incomplete low-profile visualized intraluminal support (LVIS) expansion: an in vitro study

BackgroundA low-profile visualized intraluminal support (LVIS) device may incompletely expand during stent deployment in tortuous vessels. However, the cause of incomplete expansion remains uninvestigated. We aimed to examine in vitro...

Offshore Deployments of Wave Energy Converters by Seabased Industry AB

Since 2008, Seabased Industry AB (SIAB) has manufactured and deployed several units of wave energy converters (WECs) of different design. The WECs are linear generators with point absorber buoy systems that are placed on the seabed, mounted on a gravitation concrete foundation. These deployments have taken place in different areas, using different deployment vessels. Offshore deployments of WECs and underwater substations have so far been complicated procedures, that were both expensive and time-consuming. The focus of this paper is to discuss these deployments in terms of economy and time efficiency, as well as safety. Because seven vessels have been used to facilitate the deployments, an evaluation on the above basis is carried out for them. The main conclusions and certain solutions are presented for the various problems encountered during these deployments and the vessel choice is discussed. It is found that the offshore deployment process can be optimized in terms of cost, time efficiency and safety with a careful vessel choice, use of the latest available technologies and detailed planning and organizing.

UNITED KINGDOM IN-SITU BURN TRIALS, LOWESTOFT, 1996

ABSTRACT On June 12, 1996, in a location 40 miles offshore of Lowestoft, an international audience gathered to watch Oil Spill Response Limited conduct the first controlled in-situ burn (ISB) in the United Kingdom. Two burns were completed using a response-prepared ISB system. The first burn involved fresh crude oil and was lit with a hand-held igniter using a standard gel mix. The second burn involved an emulsified crude and was lit using the Helitorch and an emulsion-breaking ignition mix. The trials were performed with the aim of determining operational practicalities under realistic conditions when responding to a weathered oil situation in an offshore location. Peripheral attention was paid to atmospheric sampling, except that air samples were collected aboard the main deployment vessel to assess worker safety. Oil analysis was carried out primarily to assess the values of the emulsion that was left as residue.

The Design and Installation of Efficient Deepwater Permanent Moorings

Industry interest in floating production systems in the Gulf of Mexico and elsewhere is increasingly pointing toward deeper water depths ranging to 10000 ft. In these waters, the moorings are an increasingly significant factor in the overall system cost. This paper presents important design considerations for deepwater mooring systems for permanently moored floating platforms. The engineering of feasible and cost-effective deepwater moorings requires substantive departures from conventional design and installation techniques. These include rethinking commonly accepted design criteria, the use of synthetic materials, alternatives to conventional catenary systems, increasing use of deeply submerged buoys, and innovative ideas for system installation. Issues addressed include: design criteria; the use of lightweight, high-strength materials such as aramid fiber rope in lieu of wire rope; analysis methods and procedures indicating the importance of quasistatic, dynamic, fatigue and probabilistic analyses; installation options and the benefits of maximizing deployment vessel options; the use of alternatives to a conventional chain/ wire catenary system; and design considerations and construction options of large-buoyancy, deeply submerged buoys.

Progress report on the ENDECO free-fall CTD (conductivity-temperature-depth sensor system)

A description is given of a vehicle system designed to meet the World Ocean Circulation Experiment (WOCE) specifications and provide a low-cost alternative for the oceanographer to using ships with hydrographic winches and dedicated conductivity-temperature-depth (CTD) systems. The vehicle is tracked using a pressure-coded acoustic pinger synchronized to an IBM-compatible computer aboard the deployment vessel. With horizontal range derived from these measurements, the vessel can maneuver to the pickup site. The system uses a temperature and conductivity sensor designed to allow at-sea calibrations in the triple point of water and gallium standard temperature cells. Water samples are obtained using 12 evacuated pyrex glass 250-ml sample bottles with special break-off fill caps. The round-trip travel time for the free-fall CTD is approximately 1 h to 6500 m compared to 4 h using conventional techniques.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>